1. Field of the Invention
This invention pertains generally to fishing rods and more particularly to a fishing rod having a polygonal cross section with integral spine which is molded in a single piece.
2. Description of the Background Art
The market for fishing rods manufactured from high tensile-strength materials, such as glass or carbon fiber, has been increased readily in recent years as the material provides a high strength to weight ratio. The most traditional fishing rods are manufactured having a circular cross-section and are generally formed in two pieces that interconnect at a ferrule. However, the circular cross section lack strength and is prone to shear and buckling under a sufficient stress.
One major disadvantage of the circular cross section is that for any given stress the top-most and bottom-most fiber in the cross section see the greatest strain to failure. If the rod is bent down, the top fiber on the circular cross section has the greatest tension; while the very bottom fiber in the circular cross section has the greatest compression. These stresses lead to premature failure. Another disadvantage to the circular cross section is that the greater the amount of stress in any direction, the greater the circular cross section tends to deform into an oval until the circular cross section collapses entirely. To counteract the deformation of the circular cross section, a redundancy of material is required, typically comprising “hoop” material used in bias with the longitudinal fibers. These hoop fibers do nothing for the action of the rod, and actually detract form the potential dynamic action of a circular cross section rod with only linear fibers. Moreover, these bias or hoop fibers promote shearing of the cross section, for when the top fiber breaks or the bottom fiber compresses, shear stress follows the bias fibers, and more readily leads to catastrophic shear failure. In addition, a serious angler is unable to obtain the proper action and level of flex across the length of the rod using a circular cross section. Accuracy is also at issue with the use of circular rod sections.
During the manufacturing of the circular cross section rod, a triangular pattern of material is wrapped around a tapered circular mandrel. This triangular lay-up method, always creates a seam on the inside and outside of the rod. Now the inside seam may run linearly down the mandrel, but the outside seam always spirals around the laid-up blank. The interior seam causes an uneven amount of fibers on one side of the blank. These uneven fibers give the finished circular rod section a linearly stiff area in the symmetrical action of the rod. The exterior seam is usually sanded or ground away; however, as the exterior laminate seam spirals around the finished blank, these uneven fibers give the finished circular rod section an asymmetric rotational action. The combination of the interior and exterior seams create what is known to serious rod makers as a spline. A rod with a spline does not have symmetrical action, and is therefore a detriment to serious accuracy. Another disadvantage of the circular cross section rod is its aerodynamics. It is common knowledge in the field of aerodynamics, that the circular rod creates more drag than any other symmetrical cross section. One major advantage of the circular rod is that these rods are readily laid-up during a simple manufacturing process. The simplicity of manufacturing of the circular cross section rod guarantees that it will always have some place in the fishing rod market, despite its relative lack of performance.
In the field of sport fishing, the rods which perhaps are subject to the highest level of scrutiny by anglers are fly fishing rods. Any fly fisherman, especially after hours of casting, recognizes the supreme importance of having very light weight equipment which provides exactly the right flexure along its entire length while not being subject to discontinuity even at the ferrules. This applies to both fresh water fly fishing and salt water fly fishing, although the relative weights of the rods significantly differ. It is also important that fly rods can be subjected to widely varying loads and environmental conditions without losing their structural integrity. Serious fly fishermen eschew the use of the cheaply designed fly rods which are manufactured with a round cross section, as it is well known that these rods cannot provide optimum feel and flex while assuring sufficient strength.
Popular fly fishing rods for serious anglers have traditionally been manufactured from bamboo sections that are joined to form a fly rod with a hexagonal cross-section. These rods have been the standard for proper feel for a number of years. Although bamboo fly rods have provided a number of advantages for serious anglers over many years, they suffer from numerous disadvantages. One major disadvantage is the weight, as the rods must be of sufficient cross section area to prevent breakage. It should be realized that forming the rods from solid pieces of bamboo does not yield an optimum strength for the material, however, the low strength of the material generally precludes anything but solid construction. The strength problem is further exacerbated in that bamboo is a natural material which is subject to variation within a single piece of wood and from one piece to another. Other disadvantages of the material is that it is a natural material that must be protected from the elements, and is subject to damage from moisture, ultraviolet light, insects, and rough conditions. Another significant aspect which is often overlooked is that the bamboo rods are formed from separate pieces of bamboo that are glued together in forming the rod section. With these glued-up sections problems arise with material property differences between the glue and bamboo, possibilities of separation of the sections especially under load bearing conditions, as well as the difficulty of creating a fly fishing rod with the proper flexure characteristics.
The advantages of the hexagonal construction have been known to anglers other than just fly fishermen. Fishing rods have been made for a range of fishing needs, from light tackle fresh water fishing to heavy tackle salt water fishing, which utilize the bamboo construction techniques and hexagonal cross sections. In recent years a few manufacturers have experimented with making synthetic bamboo rods. One example is in the area of deep sea fishing rods. The construction of these rods is typically very similar to that of the bamboo, wherein triangular composite sections are laid-up and then glued together to form the hexagonal cross-section characteristic of bamboo rods. In another construction technique a group of “T-shaped” composite sections are laid-up and then the finished sections are glued together to form a hexagon. All of these rods suffer from the bulk of disadvantages common to bamboo rods, while they cannot be readily manufactured in the small cross sections necessary to compete in the fly rod fishing market. Another example used as a fly rod, is constructed with a laminate of carbon fiber bonded to a structural foam. Tapered triangles are machined from this laminate and bonded together in a similar technique as the split cane bamboo rod. Composing a rod with a carbon fiber shell around a foam core. These have certain theoretical advantages over the circular cross section rod; however, they are solid and heavy in comparison. They also fatigue at the glue seams, and since the only structure stopping the collapse of the cross section is structural foam, they have proven to soften and deaden in action over time with repeated use.
Accordingly a need exists for a fishing rod having a high strength to weight ratio which provides a desired flex profile and feel in addition to high durability. The fishing rod of the present invention fulfills those needs as well as others and overcomes the disadvantages inherent in the traditional construction and current composite structures.